1. Field of the Invention
The present invention relates to an antenna apparatus and a method for manufacturing the antenna apparatus.
2. Description of the Background Art
As a conventional antenna apparatus, there has been a tri-plate feed type planar antenna in which a tri-plate transmission line is used in order to enhance antenna efficiency and to achieve a low-loss feeding line. As a method for manufacturing such a tri-plate feed type planar antenna, the following manufacturing method has been proposed. That is, there is a method for manufacturing a tri-plate feed type planar antenna, in which a film substrate having a antenna circuit formed thereon is mounted on a surface of a ground conductor so as to provide a lower dielectric body interposed therebetween, and in which a slot board having a plurality of slot apertures is mounted on a surface of the film substrate such that an upper dielectric body is interposed therebetween, whereby the film substrate and the slot board are fixed. The method includes the steps of: arranging a seat portion on a desired position of the ground conductor so that the slot board and the ground conductor are held separated from each other by a predetermined distance; arranging holes which penetrate from the slot board through the seat portion; inserting rivets through the holes, thereby fixing the ground conductor and the slot board together by  caulking the rivets projecting upwardly from the slot board or downwardly from the ground conductor, or by press-fitting the rivets from above the slot board. Accordingly, it is possible to uniformly maintain a holding distance between the ground conductor and the slot board, and thus a tri-plate feed type planar antenna having a satisfactory antenna characteristic can be manufactured at a lower cost and in a shorter period of time than the conventional art (for example, see Paragraph [0009], and FIG. 1, FIG. 2 of Japanese Laid-Open Patent Publication No. 07-273536, hereinafter referred to as Patent document 1).
Since the conventional tri-plate feed type planar antenna is configured as described above, and is fixed by using the rivets, the number of parts is increased. Moreover, in order to prevent occurrence of gaps and distortion, and in order to reduce variation occuring in processing of the component parts, a sophisticated processing technique is required.